st: RE: generate a varaible from date

sort companyid
by companyid: gen variable = _n
presumably, but you'd need to do something different if there are gaps in any sequence ...?
-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu on behalf of 21443017
Sent: Tue 04/08/2009 11:00
To: statalist@hsphsun2.harvard.edu
Subject: st: generate a varaible from date
Dear All,
How do I generate a variable which equals 1 for the first month the company
enters the dataset, equals 2 for the second month the company enters the
dataset etc...
It is an unbalanced panel, so every company starts from a different date.
I have an example of the dataset below,
companyname companyid date
date_s variable
Agra and Masterman's ltd 1 01-03-1965 -1138
1
Agra and Masterman's ltd 1 01-04-1965 -1137
2
Agra and Masterman's ltd 1 01-05-1965 -1136
3
Agra and Masterman's ltd 1 01-06-1965 -1135
4
Agra and Masterman's ltd 1 01-07-1965 -1134
5
Agra and Masterman's ltd 1 01-08-1965 -1133
6
Agra and Masterman's ltd 1 01-09-1965 -1132
7
Agra and Masterman's ltd 1 01-10-1965 -1131
8
Agra and United Service ltd 2 01-03-1959 -1210
1
Agra and United Service ltd 2 01-04-1959 -1209
2
Agra and United Service ltd 2 01-05-1959 -1208
3
Agra and United Service ltd 2 01-06-1959 -1207
4
Agra and United Service ltd 2 01-07-1959 -1206
5
Agra and United Service ltd 2 01-08-1959
-1205 6
Agra and United Service ltd 2 01-09-1959 -1204
7
Agra and United Service ltd 2 01-10-1959 -1203
8
Agra and United Service ltd 2 01-11-1959 -1202
9
Agra and United Service ltd 2 01-12-1959 -1201
10
"Variable" is the variable that I want to generate from the date.
Many Thanks for your help.
Best Wishes
Wenwen
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